Process for thermally cracking hydrocarbons

ABSTRACT

IN THERMAL CRACKING OF HYDROCARBONS BY BRINGING PETROLEUM HYDROCARBONS INTO CONTACT WITH A HIGH TEMPERATURE HEAT MEDIUM TO EFFECT THERMAL CRACKING OF THE HYDROCARBONS, A THERMAL CRACKING APPARATUS EQUIPPED WITH AN ULTRASONIC WAVE GENERATOR IS APPLIED TO GIVE A MIXTURE OF THE PETROLEUM HYDROCARBONS AND THE HIGH TEMPERATURE HEAT MEDIUM IN THE THERMAL CRACKING REACTION ZONE ULTRASONIC WAVE VIBRATION HAVING A POWER OF 0.01-10 WATTS/CM.2 AND A FREQUENCY OF 1-800 KHZ. THE ULTRASONIC WAVE GENERATOR IS SO DESIGNED THAT IS MAY BE PROTECTED FROM THE HIGH TEMPERATURE HEAT MEDIUM BY A FLUID MAINTAINED AT A TEMPERATURE LOWER THAN THAT OF THE MEDIUM. WHEN PETROLEUM HYDROCARBONS ARE THERMALLY CRACKED BY APPLICATION OF A THERMAL CRACKING APPARATUS EQUIPPED WITH SUCH AN ULTRASONIC WAVE VIBRATOR, BUILD-UP OF CARBON OR COKE ON THE WALL OF REACTION CHAMBER IS EFFECTIVELY PREVENTED AND THE YIELD OF THE THERMALLY CRACKED PRODUCT IS INCREASED.

June 25, 1974 SABURO HOR! PROCESS FOR THERMALLY CRACKING HYDROCARBONS 2Sheets-Sheet l Filed Sept.

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INVENTOR J14 [311 R0 Hum I CWJ ddku ATTORNEY June 25, 1974 SABURO HORI3,819,740

PROCESS FOR THERMALLY CRACKING HYDROCARBONS Filed Sept. 2. 1971 2Sheets-Sheet 2 FlG. 3

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ATT RNEY United States Patent Oflice 3,819,740 Patented June 25, 19743,819,740 PROCESS FOR THERMALLY CRACKING HYDROCARBONS Saburo Hori,Iwalri, Japan, assignor to Kureha Kagaku Kogyo Kabushilri Kaisha, Tokyo,Japan Filed Sept. 2, 1971, Set. No. 177,384 Claims priority, applicationJapan, Sept. 3, 1970, 45/ 76,654 Int. Cl. C07c 11/24 US. Cl. 260-679 R 6Claims ABSTRACT OF THE DISCLOSURE In thermal cracking of hydrocarbons bybringin petroleum hydrocarbons into contact with a high temperature heatmedium to effect thermal cracking of the hydrocarbons, a thermalcracking apparatus equipped with an ultrasonic wave generator is appliedto give a mixture of the petroleum hydrocarbons and the high temperatureheat medium in the thermal cracking reaction zone ultrasonic wavevibration having a power of 001- watts/cm. and a frequency of 1-800 kHz.The ultrasonic wave generator is so designed that it may be protectedfrom the high temperature heat medium by a fluid maintained at atemperature lower than that of the medium. When petroleum hydrocarbonsare thermally cracked by application of a thermal cracking apparatusequipped with such an ultrasonicwave vibrator, build-up of carbon orcoke on the wall of reaction chamber is effectively prevented and theyield of the thermally cracked product is increased.

BACKGROUND OF THE INVENTION This invention relates to a process forthermally cracking petroleum hydrocarbons with the application ofultrasonic wave energy and also to an apparatus for conducting such aprocess.

It is known that in a process for producing useful hydrocarbons such asolefins which comprises blowing hydrocarbon stocks such as petroleumhydrocarbons, especially crude oil, heavy oil and light oil, directlyinto a high temperature gaseous heat medium maintained at 800 C. orhigher thereby subjecting the hydrocarbon mixture to thermal crackingreaction, heavy hydrocarbons are coagulatcd or built up at the placewhere said hydrocarbon stocks are mixed with the heat medium or on thewall surface of the cracking reaction chamber, whereby the heavyhydrocarbons are carbonized or coked, thus resulting in clogging of thereaction apparatus.

Application of a variety of devices to the wall surface of the reactionchamber has been proposed in the prior art to overcome the problemdescribed above. However, all of these devices incur heat loss due tointroduction of other substances and thus can hardly be dismounted fromthe chamber after completion of the thermal cracking reaction.

It is an object of this invention to overcome the drawbacks of suchknown conventional processes and to provide an advantageous process forthermally cracking petroleum hydrocarbons without the thermal crackingreaction being affected.

It is a further object of this invention to provide a thermal crackingapparatus suitable for attaining said object.

SUMMARY OF THE INVENTION We have found that the above-mentioned objectscan effectively be attained by applying ultrasonic wave vibration withina given range of frequencies to a mixture of petroleum hydrocarbons andthe high temperature gaseous heat medium.

The ultrasonic wave vibration used in accordance with this invention iswithin the range of 1-800 kHz. and its power in terms of energy (joule)transmitted per unit area (cm. )/unit time (see), i.e. watt/cmcorresponds to 0.01-10. In the event ultrasonic Wave vibration of afrequency outside the above-mentioned range is applied, the advantageouseifect will be reduced and coke formed during the reaction will beaccumulated on the wall of reaction chamber. Thus, it is necessary tolimit the frequency of ultrasonic Wave used according to this inventionto said range. This may be attributed to the fact that if the frequencyexceeds the above mentioned range, its power will be attenuated in thecourse of application of ultrasonic wave so that eifective vibrationcannot be transmitted.

The ultrasonic wave generator which is used to transmit ultrasonic wavevibration to the thermal cracking apparatus according to this inventionmay be an electrical or mechanical generator. A ferrite vibrator ornickel vibrator is preferable from the viewpoint of its strength, heatstability and number of frequency. A rotary siren is suitable as amechanical ultrasonic wave generator but its use necessitatesintroduction of pressurized air into the reaction apparatus so thatmodification of the apparatus is required. In accordance with thisinvention, there is provided an apparatus which enables effectivetransmission of ultrasonic wave vibration to the wall of reactor withoutrequiring any special modification of the reaction apparatus itself.

The apparatus used in this invention comprises a thermal crackingreactor and an ultrasonic wave generator disposed perpendicularly to theexterior wall of the reactor and having a diaphragm connected through ahorn duct to the vibrator. In practice, the ultrasonic wave generator isprotected With a fluid maintained at a temperature lower than that ofthe high temperature heat medium used in thermal cracking. Theultrasonic wave vibration is transmitted through such fluid.

A thermal cracking apparatus using a rotary siren may also be utilizablefor this invention. In this case, a rotary siren is mounted on the topof the apparatus and a porous plate and an outlet provided at the upperpart than the porous plate for introducing a pressurized fluid needed todrive the rotary siren are disposed between the rotary siren and aninlet for the high temperature heat medium to be introduced into thereaction chamber. In this apparatus, the pressurized fluid serves toprotect the ultrasonic Wave generator from high temperature.

In general, ultrasonic wave energy is applied at ordinary temperaturesor relatively low temperatures. According to this invention, however,ultrasonic wave can be applied at the high temperatures maintained inthe thermal cracking of hydrocarbons with the ultrasonic wave generatorprotected as described above.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1 and 2, amixture of a hydrocarbon stock and a heat transfer medium is passedthrough a reactive chamber wherein the thermal cracking reaction iscarried out in the reaction chamber 1. The reaction chamber 1 issurrounded by refractory material 2.

Four ultrasonic wave generator vibrators are arranged symmetricallyaround the reaction chamber.

Each ultrasonic wave generator comprises a diaphragm 4 mounted to theexterior peripheral side of an adiabetic material 3 present at the outerside of a refractory material 2, the diaphragm being connected through ahorn 5 to a vibrator 6.

The diaphragm 4 is maintained at a high temperature by supplying steamheated at 800 C. from an inlet 8 in the outer cylindrical jacket 7 anddischarging the steam from an outlet 9. The thermal cracking reaction ofcrude oil with superheated steam was carried out using such 3 apparatusWith the frequency and power of ultrasonic wave energy being varied. Theresults are shown in the table below. For comparison, the resultsobtained by performing the thermal cracking under the same conditionsbut without application of ultrasonic wave vibration are also shown inthe table.

Thermal cracking conditions:

Starting material-Ceria crude oil, 1,000 liters/hr. Steam-2,000 0.,1,400 kg./hr. Reaction temperature-1,100 C.

Reaction time-0.005 see.

Yield of acetylene- Amount of Ultrasonic wave ethylene coke built up(W./cm. 10 kHz.) (wt. percent) (kg. feed) None. 48. 7. 2 0. 54. 1 0. 8

Referring to FIG. 3, a rotary siren 14 made of a heatresisting materialis mounted on the top of the reactor and a high temperature heat mediumis introduced from an inlet 10 above the reaction chamber 18 into alarge cavity 11 in the upper portion of the reaction chamber 18. Thehigh temperature heat medium is brought up to a steady flow rate in thelarge cavity and then mixed with oily hydrocarbons introduced from aninlet 12 fitted to an entrance of a lower constricted portion 13 of thereaction chamber 18. The mixture then flows to the lower constrictedportion 13 of the reaction chamber 18 where thermal cracking of thehydrocarbons takes place.

In the course of thermal cracking, vibration generated from a rotarysiren 14 is transmitted to the wall of the reactor 18 and gaseousreaction mixture thereby effects homogeneous mixing action between theoily hydrocarbons and the high temperature heat medium and prevention ofbuild-up of coke and carbon on the wall of reactor through vibration ofthe wall. A pressurized fluid introduced from an inlet 15 of the rotarysiren 14 is forced into the upper part of the reaction chamber 18 by theaction of the rotary siren 14. Mixing of the pressurized fluid with thehigh temperature liquid must be avoided to prevent disturbance of thetemperature distribution in the reaction chamber 18. To avoid suchmixing a porous plate 16 and an outlet 17 are disposed above the inlet10 for the high temperature fluid to permit transmission of vibrationenergy to the heat transfer medium while preventing loss of vibrationenergy in as far as possible. Gases heated as high as possible andcapable of protecting the rotary siren from injury, such as steam, aresuitable for use as the pressurized fluid in the rotary siren 14.

When Ceria crude oil was thermally cracked with steam superheated at2000 C. using the apparatus of this invention, it was observed that theyield of olefins in the experiments where no ultrasonic wave energy wasapplied was 48% (by weight) based on the starting oils, whereas theyield in the experiments using ultrasonic wave energy was as high as49-50% In the latter case, build-up of coke on the wall of r a to was otb e ved,

The most effective results were obtained in said example where steamheated at 300 C. was used as the pressurized fluid and ultrasonic wavehaving a power of 0.01- 0.3 w./cm. and a frequency of 1-50 kHz. wasused.

As is evident from the foregoing, application of ultrasonic vibrationaccording to this invention serves to minimize remarkably the amount ofcarbon and coke formed on the wall of the reaction chamber and toincrease Significantly the yield of olefins formed by the thermalcracking of hydrocarbons.

What is claimed is:

1. A process for thermally cracking hydrocarbons comprising mixing thehydrocarbons with a heat exchange medium at a temperature suflicient tocrack the hydrocarbons, and subjecting the mixture to ultrasonic wavevibrations supplied at 0.01-10 watts/cm. and at a frequency of 1-800kHz.

2. The process of claim 1 wherein said ultrasonic wave vibration issupplied by a generator and additionally comprising cooling saidgenerator by contacting said generator with a fluid maintained at atemperature lower than that of said heat exchange medium.

3. A process of claim 2 wherein said fluid is superheated steam. I

4. A process of claim 2 wherein said superheated steam is at atemperature of at least 800 C.

5. A process for thermally cracking hydrocarbons comprising: mixing thehydrocarbons with a heat exchange medium at a temperature sufficient tocrack the hydrocarbons in a reaction chamber; and subjecting the mixtureto ultrasonic wave vibration effective to prevent any build-up of carbonor coke on the walls of said reaction chamber.

6. A process for thermally cracking hydrocarbons comprising: mixing thehydrocarbons with a heat exchange medium at a temperature suflicient tocrack the hydrocarbons in a reaction chamber; and subjecting the mixtureto ultrasonic wave vibration effective to prevent any build-up of carbonor coke on the walls of said reaction chamber by means of an ultrasonicgenerator; cooling said generator by contacting 'said generator with afluid maintained at a temperature lower than that of said heat exchangemedium.

References Cited UNITED STATES PATENTS 3,268,432 8/1966 Nance 204-462 S1,811,195 6/1931 Watson 208- 3,557,241 l/197l Kivlen et al. 260- 683FOREIGN PATENTS 813,319 5/1969 Canada 204-162 DELBERT E. GANTZ, PrimaryExaminer J. M. NELSON, Assistant Examiner US. Cl. X.R.

TED STATES PEEE IQT omcE CERTIFICATE OF QURECTEN Patent No. 3,819,740Dated June 25, 1974 Inventor(s) Saboru Hori It is certified that errorappears in the above-identified patent: and that said Letters Patent arehereby corrected as shown below:

IN THE SPECIFICATION:

Column 3, line 20, after "reactor" insert --9-;

line 57, "49-50%" should read -495 4%.

Column 4, line 25, "claim 2" should read claim 3--.

Signed and sealed this 17th day of September 1974.,

(SEAL) Attest:

c MARSHALL DANN McCOY M. GIBSON JR.

Commissioner of Patents Attesting Officer CPM PC3-1050 0-69)

